At present, state-of-the-art 100 Gb/s (100 G) optical transport work is occurring in two areas: 1) transmission and modulation format development and 2) framing and standards body work required to define 100 G optical transport framing and multiplexing standards. Transmission and modulation format development falls into two categories: 1) 100 G serial optical transmission as demonstrated by network gear providers and other researchers performing 100 G optical transmission “hero” experiments, which focus on the accumulation of knowledge but not necessarily efficiency or cost-effectiveness, and 2) realistic transmission and modulation schemes that are based on present and future optical and electronic technologies, which typically involve transmission and modulation schemes that attempt to provide greater spectral efficiency, solve dispersion problems, and limit baud rates by providing multiple bits-per-symbol encodings and/or by using enhanced forward error correction (FEC) schemes, such as duo-binary modulation, Differential Phase Shift Keying (DPSK), Differential Quadrature Phase Shift Keying (DQPSK), and the like.
In general, standards bodies are looking several years into the future to define framing formats (i.e. Optical Transport Unit 4 (OTU4) in International Telecommunications Union (ITU-T) Study Group 15), backplane interface standards, and multiplexing schemes, which are unrealizable for 100 G optical transport today but will become feasible in the future. Thus, for network providers that desire 100 G optical transport solutions sooner rather than later, a disconnect exists.
At present, state-of-the-art 100 G optical transmission systems/methods do not exist in deployed networks. They are, however, actively being researched and designed to address the need for ever-increasing packet bandwidth and logical flow requirements. Long-haul 100 G serial optical transmission is possible but very unrealistic today given present optical and electronic technologies, and the same is true for the foreseeable future. Coupled with the forthcoming OTU4 100 G optical framing standard, the stage is set for present optical and electronic technologies to fall short in delivering an efficient and cost-effective 100 G optical transport system that suits the needs of today's bandwidth-hungry network providers. Thus, what is needed in the art is an approach that preserves standard framing formats and interoperability while enabling spectrally efficient 100 G optical transport today.